The present invention relates to a pig segment for the active advance of a pig in, in particular, elongate hollow bodies, preferably in gas and oil pipelines, with a drive which comprises at least one motor, at least one supporting element via which the pig segment can be supported on an inside of the hollow body, and a carrying element which is movable by the motor along a longitudinal axis of the pig segment. Furthermore, the invention relates to a pig comprising such a pig segment.
Larger industrial plants contain a multiplicity of different pipes and pipeline connections which typically, in addition to running horizontally, also run in a direction perpendicular to the underlying surface or in an arcuate manner with components in a direction perpendicular to the underlying surface. These elongate hollow bodies, which are generally circular or approximately circular in cross section, but may also have sections with polygonal cross sections, have to be maintained and optionally renovated from time to time, and therefore inspection devices in the form of cleaning or inspection pigs are sent through the pipes at intervals. In the absence of a working medium, such as, for example, gas, water or oil, the pigs have to be moved actively through the elongate hollow bodies.
DE 697 23 791 T2 shows a pig segment according to the precharacterizing clause of claim 1, in which the supporting element is extendable via a first motor and independently of the further motor, which is provided for the advance of the pig along a longitudinal axis. The supporting forces with which the pig can be supported against the pipe wall are limited by the construction used and are dependent on the motor which can push a wedge against a guide roller. In the most unfavorable case, this may result in the support beginning to slip in the case of pipe sections running vertically or perpendicularly and in particular with simultaneous curvatures when the friction of further parts of the pig that bear against the inner wall of the pipe result in increased shearing forces or when heavy loads are to be pulled through the pipe.